Number of Participants With Clinical Response at Week 6 [ Time Frame: Week 6 ]

Clinical response at Week 6 was defined as a reduction from baseline in the Crohn's Disease Activity Index (CDAI) score of greater than or equal (>=) 100 points (in general, CDAI score ranges from 0 to approximately 600; higher score indicates higher disease activities). Participants with a baseline CDAI score of > = 220 to less than or equal (< =) 248 were considered to be in clinical response if a CDAI score of less than (<) 150 was attained. A decrease in CDAI score over time indicates improvement in disease activity.

Number of Participants in Clinical Response at Week 8 [ Time Frame: Week 8 ]

Clinical response at Week 8 was defined as a reduction from baseline in the CDAI score of greater than or equal (>=) 100 points (in general, CDAI score ranges from 0 to approximately 600; higher score indicates higher disease activities). Participants with a baseline CDAI score of > = 220 to less than or equal (< =) 248 were considered to be in clinical response if a CDAI score of less than (<) 150 was attained. A decrease in CDAI score over time indicates improvement in disease activity.

70-point response is defined as at least 70 points reduction in CDAI score (in general, CDAI score ranges from 0 to approximately 600; higher score indicates higher disease activities). The CDAI score is used to quantify the symptoms of participants with Crohn's Disease. A decrease in CDAI over time indicates improvement in disease activity.

Number of Participants With CDAI 70 Point Response at Week 3 [ Time Frame: Week 3 ]

70-point response is defined as at least 70 points reduction in CDAI score (in general, CDAI score ranges from 0 to approximately 600; higher score indicates higher disease activities). The CDAI score is used to quantify the symptoms of participants with Crohn's Disease. A decrease in CDAI over time indicates improvement in disease activity.

This study (UNITI-2) will compare the effects (both positive and negative) of an initial treatment with ustekinumab to a placebo over 8 weeks in patients with moderately to severely active Crohn's disease.

Detailed Description

This study (CNTO1275CRD3002 or "UNITI-2") examines ustekinumab (an antibody medication that inhibits the inflammatory proteins IL-12 and IL-23) versus a placebo (otherwise identical except without the ustekinumab antibody) given intravenously (by an IV) in adults with moderately to severely active Crohn's disease. Ustekinumab (also known as Stelara) is approved as a treatment for the skin condition of moderate to severe plaque-type psoriasis, but this study will examine if ustekinumab can provide benefit in Crohn's disease and also assess for any risks or side effects. Both the positive and negative outcomes of IV placebo versus two different doses of IV ustekinumab will be tracked and compared over eight weeks, in approximately 612 patients who have previously failed or were intolerant to corticosteroids or immunomodulators (methotrexate, azathioprine, or 6-mercaptopurine) or are dependent on corticosteroid medications. Patients enrolling in this study will be assigned to one of the 3 treatment groups by chance (randomly, like rolling dice), and all will receive a single IV administration of study agent at the first study visit (after the screening period), and then will be asked to return for 3 additional visits through Week 8. Patients who complete this study through the Week 8 visit and remain eligible can enter the maintenance study (CNTO1275CRD3003 or "IM-UNITI"), where they will receive additional study agent, including the administration of ustekinumab in patients who receive placebo in this study and have not had improvement in their Crohn's disease. Patients who do not enter the CNTO1275CRD3003 study will have a final safety follow-up visit approximately 20 weeks after they received study agent when they entered into this study at the Week 0 visit. .All patients will receive a single intravenous (IV) administration of study drug (placebo or ustekinumab) at the start of the study.There are 3 treatment groups in this study: Group 1: Placebo; Group 2: ustekinumab 130 mg, Group 3: weight-range based ustekinumab doses approximating ustekinumab 6 mg/kg: 260 mg (weight <= 55 kg), 390 mg (weight > 55 kg and <= 85 kg), and 520 mg (weight > 85 kg).

Has failed conventional therapy as demonstrated by having received corticosteroids and/or immunomodulators(ie, AZA, MTX, or 6-MP) at adequate therapeutic doses OR Have a history of failure to respond to or tolerate an adequate course of corticosteroids and/or immunomodulators (ie, AZA, MTX, or 6-MP) at adequate therapeutic doses OR Is corticosteroid dependent or has had a history of corticosteroid dependency AND Has not previously demonstrated failure of or intolerance to 1 or more TNF-antagonist therapies (ie, infliximab, adalimumab, or certolizumab pegol) per study criteria